The gelada (Theropithecus gelada, , ), sometimes called the bleeding-heart monkey or the gelada baboon, is a species of Old World monkey found only in the Ethiopian Highlands, living at elevations of above sea level. It is the only living member of the genus Theropithecus, a name derived from the Greek root words for "beast-ape" (θηρο-πίθηκος : thēro-píthēkos). Like its close relatives in genus Papio, the baboons, it is largely terrestrial, spending much of its time foraging in grasslands, with grasses comprising up to 90% of its diet.
It has buff to dark brown hair with a dark face and pale eyelids. Adult males have longer hair on their backs and a conspicuous bright red patch of skin shaped like an hourglass on their chests. Females also have a bare patch of skin but it is less pronounced, except during estrus, when it brightens and exhibits a "necklace" of fluid-filled blisters. Males average and females average in weight. The head-body length is with a tail of .
The gelada has a complex multilevel social structure. Reproductive units and male units are the two basic groupings. A band comprises a mix of multiple reproductive units and male units; a community is made up of one to four bands. Within the reproductive units the females are commonly closely related. Males will move from their natal group to try to control a unit of their own and females within the unit can choose to support or oppose the new male. When more than one male is in the unit, only one can mate with the females. The gelada has a diverse repertoire of vocalizations thought to be near in complexity to that of humans.
The population of geladas is thought to have dropped from 440,000 in the 1970s to 200,000 in 2008. Despite the heavy loss, it is listed as least concern by the International Union for Conservation of Nature.
Taxonomy and evolution
Since 1979, the gelada is customarily placed in its own genus (Theropithecus), though some genetic research suggests that this monkey should be grouped with its baboon (genus Papio) kin; other researchers have classified the species even more distantly from Papio. While Theropithecus gelada is the only living species of its genus, separate, larger species are known from the fossil record: T. brumpti, T. darti and T. oswaldi, formerly classified under genus Simopithecus. Theropithecus, while restricted at present to Ethiopia, is also known from fossil specimens found in Africa and the Mediterranean into Asia, including South Africa, Malawi, the Democratic Republic of the Congo, Tanzania, Uganda, Kenya, Algeria, Morocco, Spain, and India (more exactly at Mirzapur, Cueva Victoria, Pirro Nord, Ternifine, Hadar, Turkana, Makapansgat, and Swartkrans).
The two subspecies of gelada are: Northern gelada, T. g. gelada Eastern gelada, southern gelada, or Heuglin's gelada, T. g. obscurus
Common name
The gelada has been referred to by other names, including the "gelada baboon", "bleeding-heart baboon", or simply "baboon", implying a monophyletic relationship with baboons, which historically included (apart from Theropithecus) the genera Papio (true baboons), and Mandrillus (mandrills and drills). Since the 1990s, however, molecular phylogenetic studies clarified relationships among papionin monkeys, demonstrating that mangabeys of the genus Lophocebus are more closely related to Papio and Theropithecus, while mangabeys of the genus Cercocebus are more closely related to Mandrillus. These findings largely invalidated any scientifically based justification for referring to mandrills and drills as baboons, as doing so while excluding the unbaboon-like Lophocebus mangabeys would create a polyphyletic group. The status of geladas was less clear and the relationships among Papio, Lophocebus, and Theropithecus continue to reflect high levels of uncertainty, which are further complicated by the discovery of the kipunji. Nevertheless, the most recent and extensive phylogenetic study to date demonstrates that, while large fractions of the genome show an alternative history, the dominant relationship across the genome supports a closer relationship between Papio and Lophocebus, with Theropithecus as the outgroup. As a close sister relationship between Papio and Theropithecus is the least-supported scenario in recent studies, "gelada baboon" and other names implying a close relationship with baboons, with increasing clarity, are not scientifically justified, leading researchers to advocate for the common name to be simply "gelada".
Description
The gelada is large and robust, and it is covered with buff to dark-brown, coarse hair and has a dark face with pale eyelids. Its arms and feet are nearly black. Its short tail ends in a tuft of hair.Napier PH. (1981). Catalogue of primates in the British museum (natural history) and elsewhere in the British Isles, part II: family Cercopithecidae, subfamily Cercopithecinae, London: British Museum (Natural History).Ankel-Simons F. (2007). Primate Anatomy: an introduction, (3rd edition), San Diego: Elsevier Academic Press. Adult males have a long, heavy cape of hair on their backs. The gelada has a hairless face with a short muzzle that looks more similar to a chimpanzee's than a baboon's. It can also be physically distinguished from a baboon by the bright patch of skin on its chest. This patch is hourglass-shaped. On males, it is bright red and surrounded by white hair; on females, it is far less pronounced, but when in estrus, the female's patch brightens, and a "necklace" of fluid-filled blisters forms on the patch. This is thought to be analogous to the swollen buttocks common to most baboons experiencing estrus. In addition, females have knobs of skin around their patches. Geladas also have well-developed ischial callosities. Sexual dimorphism is seen in this species; males average 18.5 kg (40.8 lb), while females are smaller, averaging 11 kg (24.3 lb).Jolly CJ. (2007). "Baboons, mandrills, and mangabeys: afro-papionin socioecology in a phylogenetic perspective", In: Primates in perspective, Campbell CJ, Fuentes A, MacKinnon KC, Panger M, Bearder SK (eds), New York: Oxford University Press pp. 240–51. The head and body length of this species is 50–75 cm (19.7–29.5 in) for both sexes. Tail length is 30–50 cm (11.8–19.7 in).
The gelada has several adaptations for its terrestrial and graminivorous (grass-eating) lifestyle. It has small, sturdy fingers adapted for pulling grass and narrow, small incisors adapted for chewing it. The gelada has a unique gait, known as the shuffle gait, that it uses when feeding.Dunbar RIM. (1977). "Feeding ecology of gelada baboons: a preliminary report", In: Primate ecology: studies of feeding and ranging behaviour in lemurs, monkeys and apes, Clutton-Brock TH (ed), London: Academic Pr. p 251–73. It squats bipedally and moves by sliding its feet without changing its posture. Because of this gait, the gelada's rump is hidden beneath, so is unavailable for display; its bright red chest patch is visible, though.
Range and ecology
Geladas are found only in the high grasslands of the deep gorges of the central Ethiopian plateau. They live in elevations above sea level, using the cliffs for sleeping and montane grasslands for foraging. These grasslands have widely spaced trees and also contain bushes and dense thickets.Iwamoto T, Dunbar RIM. (1983). "Thermoregulation, habitat quality and the behavioural ecology of gelada baboons", J Anim Ecol 52(2):357-66. The highland areas where they live tend to be cooler and less arid than lowland areas. Thus, the geladas usually do not experience the negative effects that the dry season has on food availability. Nevertheless, in some areas, they do experience frost in the dry season, as well as hailstorms in the wet season.
Geladas are the only primates that are primarily graminivores and grazers – grass blades make up to 90% of their diet. They eat both the blades and the seeds of grasses. When both blades and seeds are available, geladas prefer the seeds. They eat flowers, rhizomes, and roots when available, using their hands to dig for the latter two. They consume herbs, small plants, fruits, creepers, bushes, and thistles. Insects can be eaten, but only rarely and only if they can easily be obtained. During the dry season, herbs are preferred over grasses. Geladas consume their food more like ungulates than primates, and they can chew their food as effectively as zebra.
Geladas are primarily diurnal. At night, they sleep on the ledges of cliffs.Crook JH. (1966). "Gelada baboon herd structure and movement: a comparative report", Symp Zool Soc Lond 18:237–58. At sunrise, they leave the cliffs and travel to the tops of the plateaus to feed and socialize. When morning ends, social activities tend to wane and the geladas primarily focus on foraging. They travel during this time, as well. When evening arrives, they exhibit more social activities before descending to the cliffs to sleep. Predators observed to hunt geladas include domestic dogs, leopards, servals, hyenas, and lammergeiers.
Behavior
Social structure
Geladas live in a complex, multilevel society similar to that of the hamadryas baboon. The smallest and most basic groups are the reproductive units, which include up to 12 females, their young, and one to four males, and the all-male units, which are made up of 2–15 males. The next level of gelada societies are the bands, which are made up of two to 27 reproductive units and several all-male units. Herds consist of up to 60 reproductive units that are sometimes from different bands and last for short times. Communities are made of one to four bands whose home ranges overlap extensively. A gelada typically lives around 15 years.Dunbar RIM. (1986). "The social ecology of gelada baboons", In: Ecological aspects of social evolution: birds and mammals, Rubenstein DI, Wrangham RW, (eds), Princeton (NJ): Princeton University Press pp. 332–51.Grüter CC, Zinner D. (2004). "Nested societies. Convergent adaptations of baboons and snub-nosed monkeys?" Prim Rep 70:1-98.
Within the reproductive units, the females tend to be closely related and have strong social bonds. Reproductive units split if they become too large. While females have strong social bonds in the group, a female only interacts with at most three other members of her unit. Grooming and other social interactions among females usually occur between pairs. Females in a reproductive unit exist in a hierarchy, with higher-ranking females having more reproductive success and more offspring than lower-ranking females. Closely related females tend to have a similar hierarchical status. Females generally stay in their natal units for life; cases of females leaving are rare. Aggression within a reproduction unit, which is rare, is usually just between the females. Aggression is more frequent between members of different reproductive units and is usually started by females, but males and females from both sides can join and engage if the conflict escalates.